Preparation of acryloxyalkylorganodisiloxanes



United States Patent f PREPARATION OF ACRYLOXYALKYL- ORGANODISILOXANES Robert L. Merker, Pittsburgh, Pa., assignor to Dow C orning Corporation, Midland, Mich., a corporation of Michigan No Drawing. Application February 1, 1957 Serial No. 637,623

7 Claims. (Cl. 260-448.?)

This invention relates to disiloxanes having acryloxy or methacryloxy groups attached to the silicon through a divalent alkylene radical of from 2 to 4 inclusive carbon atoms. V I

Conventional organosiloxane resins and rubbers generally consist of polymeric units of the formula R,,SiO T where x has an average value of from about 0.8 to about 2 and R represents'monovalent hydrocarbon radicals or halogenated derivatives thereof. Such polymers have become well known articles of commerce. One of the difiiculties with these polymers has been the high temperature and long heating schedule necessary to cure them to a satisfactory degree. Another difliculty has been due to the fact that ordinarily an organic solvent solution of the resinous polymers must be employed to handle them in the intermediate stage of polymerization in which they are marketed. Many efforts have been made to modify these silicones so that solventless thermosetting resins could be produced. I

One of the primary objects of this invention is to provide a modified siloxane which can be set at low temperatures in a short period of time, and which can be employed in the fabrication of elastomers or in solventless form as dipping varnishes, impregnating resins, and the like. Other objects will be apparent from the'following specification.

This invention specifically relates to disiloxanes of the formula 1 in which n is an integer of from 2 to 4 inclusive, R is selected from the group consisting of hydrogen and methyl radicals, and R is a monovalent hydrocarbon radical free of aliphatic unsaturation. The R radicals can be the same or different radicals.

It has been shown in my copending application Ser. Neg 431,295, filed May 20, 1954, now US. Patent No.

2,793,223, issued May 21, 1957, that siloxanes containing units of the formula (CH =CROOOCH )R,,,SiO i l a I I T where R and R are as above defined and'm is l or 2, can be prepared by reacting, e.g., compounds of the formula ClGH R,,,SiO

with sodium or potassium salts of acrylic or methacrylic acid. Although such siloxanes have very desirable properties, their commercial development has been somewhat curtailed by the difiicultiesfinherent in the commercial production of; the necessary halomethylsiloxane intermediates. Til clatter are prepared by the halogenation of the methyl'ra'dical attachedto siliconQahd there is a Z,2Z,8G? Patented Jan. 26, 1960 with acrylic or methacrylic acid (or a mixture of both acids if a mixed product is desired), followed by equilibrating the reaction product with (R' Si) O, preferably in the presence of an acid catalyst. The first step in this process might be expected to produce the compound OIQSiR (CH ),,OOCRC=CH The latter should be a distillable compound, and thus readily isolated. Actually, however, it has been found that no distillable product is formed from the step in question, and a higher molecular weight polymer of unknown configuration is apparently the only product of this first step.

The second step can be carried out by merely contacting the first reaction product with the hexaorganodisiloxane at room temperature in the present of a suitable acidic organosiloxane rearrangement catalyst, a number of which are well known to the art. A preferred catalyst is concentrated sulfuric acid, and exceedingly good results are obtained by using this in conjunction with trifiuoroacetic acid. Amounts of catalyst in the range of about 1 to 5 percent by weight of total acid based on the total siloxanes present are suitable, although this range is by no means critical. The equilibration can be speeded up by carrying it out at elevated temperatures, e.g. up to about C., and less catalyst is required at such temperatures.

Ifdesired, the first and second steps above can be carried out simultaneously. Thus the dialcohol, the

acrylic or methacrylic acid, the hexaorganodisiloxane, and the acid catalyst can all be mixed together and allowed to stand at room temperature, then the mass Washed and distilled. Preferably a polymerization inhibitor for the unsaturated acid is also added.

The dialcohol employed above is best prepared by the alcoholysis of a corresponding diacyloxy compound, e.g. O[SiR' (CI-i OOCCl-l The step can be carried out by contacting (preferably at reflux temperature) thediacyloxy compound with an alcohol such as methanol or ethanol in the presence of a basic catalyst such as NaOH or KOH when n is 2, or in the presence of either a basic catalyst. or an acid catalyst such as H 80 when n is 3 or 4. The diacyloxy compound where n is 3 or 4 is best prepared by reacting (R' HSi) O with e.g. allyl acetate or its next higher homologue, the acetate of allylcarbinol (3-buten-l-ol). Typical disiloxanes which can be used in this step are [(CH HSi] O, [CH (C H )HSi] O, and [(C H HSi] O. This reaction can be carried out in the presence of chloroplatinic acid as a catalystlpreferably in amounts of from 1 1 0- to 1 10 mol per mol of siloxane) at temperatures of e.g. 80 to C. Whenn in the diacyloxy compound is 2 it is preferable to react RgHSiCl with vinyl acetate, using the same catwhich R is methyl orphenyl.

' Analter'native process for the production of those cbm (CH SiOSi(CH 3 (CH C H SiOSi (C H CH e s z s s e s) z and (CH C H SiOSi(C H The compounds of this invention are readily polymerized e.g. by heating them in the presence of peroxy type vinyl polymerization catalysts. Such catalysts are well known, and include benzoyl peroxide, t-butyl perbenzoate, t-butyl peracetate, and the like. The low viscosity of the unpolymerized product gives it utility as an impregnating varnish, potting compound for intricate or diflicultly accessible areas, etc. without need for dilution with an organic solvent. The polymerized material is a tough elastic solid.

The compounds of this invention can also be copolymerized with organic vinylic type resins, or can be incorporated into conventional organosiloxanes of the general formula tacting the two polymers, at elevated temperatures if desired, in the presence of a siloxane rearrangement catalyst such as H 80 The resulting copolymer then contains the CH =CRCOO(CH ),,SiE units in its siloxane network, and is thus readily polymerized through the acrylic portion of the molecule. The distillable nature of the inventive compounds makes the isolation of pure material practical, so that the amounts incorporated into other copolymers can be carefully controlled.

The following examples are illustrative only. All parts mentioned are parts by weight.

Example 1 CH =CHCOOCH CH CH (CH SiOSi(CH 3 was obtained, boiling at 105 107 C./i0 mm. Hg, n 1,4222, (I 0901, R 0.2821 (calculated value 0.2822).

Example 2 The procedure of Example 1 was employed on a mixture containing parts (0.2 mol) 0 [Si CH CH CH CH OH] 2 35.8 parts 96% pure methacrylic acid, 3.4 parts hydroquinone, 64.8 parts hexamethyldisiloxane, 3.4 parts trifiuoroacetic acid and 3.4 parts sulfuric acid. The product CH =C (CH COOCH2CHZCHQ(CH3) SiOSi (CH 3 was obtained, boiling at 120-125 C/l0 mm. Hg, 11 1.4255, (1 0.901, R 0.2841 (calculated value 0.2841).

Example 3 A mixture of 76.4 parts O[Si(CI-l CH CH CH OI-l] 52.3 parts methacrylic acid, 5 parts hydroquinone, 5 parts sulfuric acid, and 66 parts benzene was heated at reflux temperature for 3 hours. Water was trapped out of the refluxing benzene-water azeotrope during this period. The reactionmass was washed until neutral, dried, and the benzene removed by flash distillation. The residue was heated to 200 C./ 3 mm. Hg in an attempt to distill a product therefrom, but no distillate was obtained. There was then added 121.5 parts hexamethyldisiloxane, 7 parts trifiuoroacetic acid, 7 parts sulfuric acid, and 7 parts hydroquinone to the above residue. The mixture was allowed to stand 3 days at room temperature, and was then washed free of water, dried, and distilled. The same product as in Example 2 was obtained, and it was found to have a saponification equivalent of 270 as compared tothe calculated value of 274.

Example 4 The procedure of the first step of Example 3 was repeated, except that acrylic acid was employed rather than methacrylic. Again it was found that no distillable product was obtained at temperatures up to about 200 C./ 3 mm. Hg. The material was then equilibrated with hexamethyldisiloxane as in the second step of Example 3, and

the acryloxypropyl substituted product of Example 1 was and if O[Sl(CH3)zCHgCHzCHgCHzOHlg is used the product is CH =C(CH C0OCH CH CH CH (CH SiOSKCH Example 6 The products of Examples 1 and 2 were individually mixed with 0.1% by weight of a,a'-azo-diiso-butyronitrile and heated at 100 C. Each formed an elastic solid polymer.

That whichis claimed is:

1. A process for the preparation of compounds of the formula CH =CRCOO(CH SiR' OSiR" where each R and each R" is a monovalent hydrocarbon radical free of aliphatic unsaturation, R is selected from the group consisting of hydrogen and a methyl radical, and n is an integer of from 2 to 4 inclusive, which comprises reacting a disiloxane of the formula O[SiR' (CH ),,OHlwhere each R and n are as above defined, by contacting said disiloxane in a liquid phase with an acid selected from the group consisting of acrylic and methacrylic acid, and reacting the reaction mass therefrom by contacting said mass in a liquid phase with a disiloxane of the formula (R" Si) O, where each R" is as above defined, in the presence of from 1 to 5 inclusive percent by weight based on the weight of the total siloxanes in the system, of an acidic organosiloxane rearrangement catalyst.

2. A process for the preparation of compounds of the formula CH =CRCOO(CH ),,SiR' OSiR" where each R and each R" is a monovalent hydrocarbon radical free of aliphatic unsaturation, R is selected from the group consisting of hydrogen and a methyl radical, and n is an integer of from 2 to 4 inclusive, which comprises contacting in a liquid phase a disiloxane of the formula O[SiR (CH ),,OH] where each R and n are as above defined, an acid selected from the group consisting of acrylic and methacrylic acid, and a disiloxane of the formula (R" Si) O where each R is as above defined, in the presence of from 1 to 5 inclusive percent by weight of an acidic organosiloxane rearrangement catalyst based on the weight of the total siloxanes in the system.

3. A process for the production of a compound of the formula where R is selected from the group consisting of hydrogen and a methyl radical, which comprises contacting a disiloxane Of the formula an acid selected from the group consisting of acrylic and methacrylic acid, and hexamethyldisiloxane, in a liquid phase and in the presence of from 1 to 5 inclusive percent by weight of concentrated sulfuric acid catalyst based on the weight of the total siloxanes present.

4. A process for the production of a compound of the formula CH CRCOO (CH Si CH Si( CH where R is selected from the group consisting of hydrogen and a methyl radical, which comprises contacting in a liquid phase a disiloxane of the formula with an acid selected from the group consisting of acrylic and methacrylic acid, and contacting the reaction mass thereof with hexamethyldisiloxane in a liquid phase and in the presence of from 1 to inclusive percent by weight of concentrated sulfuric acid catalyst based on the weight of the total siloxanes.

5. The method which comprises contacting a disiloxane of the formula O[Si(CH CH CH CH OH] methacrylic acid, and hexamethyldisiloxane, in a liquid phase and in the presence of from 1 to 5 inclusive percent by Weight of concentrated sulfuric acid catalyst based on the weight of the total siloxanes; removing said acid catalyst from the reaction mass; and separating the product CH =CMeCOO(CH Si(CH OSi(CH where Me represents a methyl radical.

6. The method which comprises contacting in a liquid phase a disiloxane of the formula O[SiR (CH ),,OH] where each R is a monovalent hydrocarbon radical free of aliphatic unsaturation and n is an integer of from 2 to 4 inclusive, with an acid selected from the group consisting of acrylic and methacrylic acid; contacting the reaction mass thereof with a disiloxane of the formula (R" Si) O in a liquid phase and in the presence of from 1 to 5 inclusive percent by weight of an acidic organosiloxane rearrangement catalyst based on the weight of the siloxanes in the system, each R" being a monovalent hydrocarbon radical free of aliphatic unsaturation; removing the acid catalyst from the reaction mass and distilling off the product where n, R, and R" are as above defined and R is selected from the group consisting of hydrogen and a methyl radical.

7. The method which comprises contacting a disiloXane of the formula O[Si(CH CH CH CH OH] an acid selected from the group consisting of acrylic and methacrylic acid, and hexamethyldisiloxane, in a liquid phase and in the presence of from 1 to 5 inclusive percent by weight of concentrated sulfuric acid catalyst based on the weight of the total siloxanes; removing said acid catalyst from the reaction mass; and distilling off the product CH =CRCOO CH Si (CH 08i CH 3 where R is selected from the group consisting of hydrogen and a methyl radical.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR THE PREPARATION OF COMPOUNDS OF THE FROMULA CH2=CRCOO(CH2)NSIR''20SIR"3, WHERE EACH R'' AND EACH R" IS A MONOVALENT HYDROCARBON RADICAL FREE OF ALPHATIC UNSATURATION, R IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND A METHYL RADICAL, AND N IS AN INTEGER OF FROM 2 TO 4 INCLUSIVE, WHICH COMPRISES REACTING A DISILOXANE OF THE FORMULAE O(SIR''2)CH2)NOH)2, WHERE EACH R'' AND N ARE ABOVE DEFINED, BY CONTACTING SAID DISILOXANE IN A LIQUID PHASE WITH AN ACID SELECTED FROM THE GROUP CONSISTING OF ARCYLIC AND METHACRYLIC ACID, AND REACTING THE REACTION MASS THEREFROM BY CONTACTING SAID MASS IN A LIQUID PHASE WITH A DISILOXANE OF THE FORMULA (R"3SI)20, WHERE EACH R" IS ABOVE DEFINED, IN THE PRESENCE OF FROM 1 TO 5 INCLUSIVE PERCENT BY WEIGHT BASED ON THE WEIGHT OF THE TOTAL SILOXANES IN THE SYSTEM, OF AN ACID ORGANOSILOXANE REARRANGEMENT CATALYST. 